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Calculating Roof Replacement

When you decide to replace your roof due to a storm or simply age or wear, you should be aware of a number of factors that can influence the cost of the roof. Like anything else you purchase there are a variety of details that influence durability, beauty, ventilation, energy-efficiency and ultimately, price.

Online tools may provide a quick and dirty ‘estimate’ for calculating the cost of a new roof, but for a more accurate cost estimate, it’s best to consult a local roofing contractor for a roof inspection. They’ll not only tell you IF you need to have your roof replaced or repaired, as well as a cost for the roof repair. If indeed a cost estimate is provided, it’s generally based on the below criteria:

Roof Size

It goes without saying, the larger the roof size, the more material and labor required. It’s probably the biggest factor in pricing a new roof.

Roof Square Footage

Real estate agents often use a square foot calculation, which doesn’t include patios, garages or entries. In addition, multiple story homes make it more difficult to quickly gauge the amount of roof square footage. A loose calculation is to multiply the length by the width of the living area from edge to edge, however some roofing companies offer a free roofing inspection and will calculate this, along with other factors, for you.

Roof Slope

Typically the steeper the slope, the more expensive the project. Laborers aren’t as efficient in constructing steeper roofs and need to consider additional safety measures.


There is typically at least 10% overage calculated into each project based on the design of the project. Areas around flashing and valleys can use more material.

Number of Roofing "Squares"

Typically contractors order roof materials in ‘squares’ which is calulated by dividing the entire roof area by 100 (1 square).

Roof Material and Quality

There is a wide range of color, durability and architectural shingles, tiles, composition material or metal options available, all of which can effect the cost.

Roof Design

Gables, Valleys and Dormers on more elaborately-designed homes or commercial buildings will effect the cost. There are often more cuts involved and more material will need to be used.

Existing Roof Condition

A roof inspection will identify whether the roof structure is adequate or whether holes, or delamination of the surface has occurred. When the underlying structure is compromised, additional work needs to be done to repair the surface before the new roof can be installed.

Geographic Area

Just like homes can tend to be more expensive in some areas, roofs too can cost more. Municipal authorities may have additional requirements in some areas and materials and labor may cost more as well.

Local Inspections or Permits

Some areas require more licensing, inspections or permits than other regions.

Labor Rates

Labor rates vary from region to region.

Materials Disposal Fees

Trash and dumpster services can vary by area.


Ventilation helps keep the temperature in your home more comfortable and helps to lower energy costs. There are a variety of ventilation options that can also influence the cost of your overall roof estimate.

For more information, or to discuss the possibility of a new roof or repair, contact Roof Smart Pro for a Free Roof Inspection today.

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